A "consent of surety" is defined by federal law as the consent a contracting party must receive from the surety on changes made to an initial contract, according to the Legal Information Institute at Cornell University Law School. In certain cases, obtaining a consent of surety is required by law.
According to the Legal Information Institute, a consent of surety is needed in all cases when additional bond is obtained from someone other than the original surety. Even if a new bond is not taken out, any contract changes that expand the scope of a project or change the price require consent. The surety is the party that guarantees payment from the contracting party to the contractor, according to Investopedia.